Method of making propellers



M. A. SMITH, JR

METHOD 0F MAKING PROPBLLERS March 27, 1934.

Filed March 18 x O W m e u n 77x n O m 3Q v 2 .2 n Q .wf .L F, m F W1 z J/ m m m m z W Patented Mar.l 27, 1934 METHOD oF MAKING PRoPELLERs Marshall A. Smith, Jr., South Bend, Ind., as-

signor to Bendix Research Corporation, East Orange, N. J., a corporation of Indiana Application March 18, 1931, Serial No. 523,552

9 Claims.

This invention relates to propellers and more particularly to hollow metal propellers.

One of the objects of the present invention isto provide a novel method of producing a hollow metal propeller blade.

Another object of the invention is to provide a novel method of manufacturing a propeller blade of the above character, from a metal tube whereby the latter is transformed during the various 10 operations, into a member forming one face of the nished blade.

Still another object is to provide in a method such as that above referred to, a novel series of steps including the removal of a portion of the wall of the tube in such a manner that the resultant Work-piece when opened will beaxially twisted in a manner corresponding to the desired angularity or pitch of the finished blade.

A further object is to provide in a method of the above character, a novel series of steps for transforming a hollow tube into a propeller blade of airfoil section, which may be effected in an extremely simple and efficient manner and at minimum cost in order to produce a light hollow propeller blade having exceptionally durable qualities.

The above and other objects will appear more fully hereinafter from the following detailed description when taken in connection with the accompanying drawing. It is 'to be expressly understood, however, that the drawing is for purposes of illustration only and is not designed as a definition of the limits of the invention, reference being had for this purposeto the appended claims.

1n the drawing:

Fig. 1 is a side view of a hollow metal tube which may be transformed into a hollow propeller blade in accordance with the present invention;

Fig. 2 is a side view of the tube after variation of the thickness of the wall thereof;

Fig. 3 is a side view of the tube showing a portion of the wall removed;

Fig. 4 is a view similar to Fig; 3. but illustrating a modified form;

Fig. 5 is a plan view of the tube illustrated in Figs. 3 or 4 after the tube has been opened and pressed into a blade member constituting one face of the nished blade;

Figs. 6, '7, 8 and 9 are transverse sections of the blade member shown in Fig. 5;

Fig. 10 is a plan View of the'cover plate or other blade member constituting the other face of the desired blade;

, walls which diverge from left to right, as viewed (Cl. .Z9-156.8)

Figs. 11, 12 and 13 are transverse sections of the blade member shown in Fig. 10;

Fig. 14 is a plan View of the finished blade;

Figs. l5, 16 and 17 are transverse sections of the finished blade; and A Fig. 18 is a transverse section of a blade illustrating a modified form.

According to the present invention, a hollow metal tube, which may be seamless if desired, is formed into a hollow light-weight propeller blade, suitable for use on aircraft, by a series of steps including removing a longitudinally extending section of the wall of the tube, opening and pressing the resultant Work-piece into`a blade member constituting one face of the blade desired to be formed, and completing the blade member by securing thereto, a second blade member forming the other face of the desired blade.

Referring more particularly to Fig. 1 of the drawing, there is disclosed therein, a hollow metal tube 18 suitable for use in forming a propeller blade in accordance with the present invention, which tube isr provided with a wall of uniform thickness. Preferably, the tube is of a diameter corresponding to the diameter of the root end of the blade which it is desired to form. in order to obviate the necessity of difficult and expensive operations upon one end of the tube in order to adapt the same to the usual split propeller hub. In order also to eliminate, as much as possible, all unnecessary joints, welds, etc., it is preferred to employ a tube of seamless character.

The tube 18 is initially machined, rolled, drawn or otherwise manipulated in any suitable manner in order to decrease the thickness of the wall circumferentially from a point adjacent one end to the other, as indicated in Fig. 2. The resultant blank is thus constituted by a cylindrical root portion 19 and an outer blade portion 20, the wall thickness of which varies from one end to the other.

In order to fashion the tube 18, thus formed, into a work-piece or blank suitable for subsequent formation into a blade member, a portion of the wall of said tube is removed from a. point adjacent.A the root end of the tube to the other to form a slot or opening 2l. As shown` in Fig. 3, the slot 21 is in the form of a tapered, longitudinally extending opening andis provided with in this figure.

A modification of the method of longitudinally slotting the wall of the tube 18 is disclosed in Fig. 4 wherein the tapered slot 22 is spirally arranged with respect to the longitudinal axis of the tube. no

that is, the slot is formed as a long pitch screw or helix, the sides thereof, however, diverging from one end toward the other in a manner similar to that described in connection with Fig. 3. A distinct advantage to be derived from the utilization of a spiral slot in the wall of the tube is that when the resultant blank is opened, the outer slotted portion of the blank will be axially twisted in such a manner that the blade face thus formed will possess the necessary angularity or pitch. It will be understood that the pitch of the spiral slot may be so proportioned that the resultant angularity of the blade face will be that required under the given conditions.

The resultant slotted blank, formed by either of the two above-described methods, is then placed in a suitable die or press in order to effect an opening and pressing of the blank to form a blade member 23 constituting a blade face of the blade which it is desired to produce. In this dieforming operation, the work-piece may be heated if desired, in any suitable manner, in order to more readily adapt the blank to the shape desired. In the event that the slotted tube illustrated in Fig. 3 is employed, it will be necessary, during this operation, to impart an axial twist to the blank in order that the blade member 23 may be provided with the necessary pitch or angularity. If, however, the tube shown in Fig. 4 is utilized, it will be unnecessary to resort to this procedure, since, as has been hereinbefore pointed out, the opening of such tube by suitable die members, will result in a blade member having the necessary angularity. Preferably, the outer end portions 24 and 25 of the blade member 23 are removed in any suitable mannerte effect a suitable rounded outer end portion 26 corresponding to the shape of the finished blade.

It will be observed that the transverse sections of the blade member 23, disclosed in Figs. 6-9, illustrate that the blade member thus formed is cambered and provided with an opening 27 which is adapted to be closed by a suitable cover plate,

which, in the particular form of the invention illustrated, is adapted to constitute the thrust face of the finished blade and which coacts with the blade member 23 to form a completed, hollow blade of aerofoil section.

In Fig. 10, there is illustrated a suitable cover plate 28 which may be employed for completing the exterior surface of the blade member 23. Preferably, this plate or blade face is uniformly tapered in thickness from one end to the other, as illustrated in the transverse sections of the plate shown in Figs. 11-13. As will be also observed from these last-named figures, the plate is also axially deformed ,or twisted in order that 'when secured to the blade member 23, the resultant blade will be provided with the required pitch.

In securing the blade face 28 to the blade member 23 to form the completed blade 29, the former is placed in such a position as to close the opening 27 and the marginal edges of the member 28 are firmly' secured to the correspondingedges of the.

tudinally extending flanges 23b which closely embrace the member 28 and extend slightly above the outer surface of this member. When it is desired to secure the members 23a and 28 together, it is only necessary to fuse the portions of the iianges protruding beyond the outer face of the member 28 and the molten metal thus produced is employed for firmly securing the two blade members together. Any uneven surfaces resulting from such operation may be ground off and the completed blade burnished and polished in any suitable manner.

There is thus provided by the present invention a novel method for producing a propeller blade from a hollow tube characterized by the provision of a minimum number of operations necessary to be performed thus resulting in a marked saving in time and expense. 'Ihe provision of the tapered slot in the wall of the hollow tube enables the formation of one-half of the desired blade in a simple and efficient manner and without the necessity of complicated and expensive apparatus for obtaining and regulating external and internal pressures heretofore considered necessary in producing propeller blades from hollow metal tubes. In one embodiment of the invention, the tapered slot is disclosed in the form of a spiral, which may be especially advantageous in that the necessity of axially twisting the resultant blade member, heretofore necessary in order to provide the necessary angularity or pitch, is avoided.

While only two embodiments of the present. invention have been illustrated and described, it will be understood that the invention is not limited thereto but may be embodied in other forms. For example, While the hollow tube has been described and illustrated as being transformed into a member constituting the camber face of the blade desired to be formed, it will be understood that the tube may be fashioned into the thrust face if desired. It will also be understood that slots of variable shapes and proportions may be provided in the wall of the tube in order to secure any specified final form and shape of blade member. Various other changes may be effected in the details of construction and method of manufacture, as will be readily understood by those skilled in the art without departing from the spirit of the invention, and reference will therefore be had to the appended claims for a definition of the limits thereof.

What is claimed is:

1. The method of making a propeller blade from a hollow tube which comprises decreasing the thickness of the wall of the tube from a point adjacent one end to the other, forming an axial opening in the wall of said tube the sides of said opening diverging from one end to the other, imparting a substantially flattened shape to that-portion of the tube provided with said I opening the width of `the resultant work-piece .corresponding to the width of the blade desired to be formed, and securing a member of varying thickness to said woi'k-piece to form the desired blade, said member corresponding in shape to the flattened portion of said work-piece.

2. A method of making a prdpeller blade including varying the thickness of the wall of a seamless metal tube, removing a substantially spirally formed section of the wall of said tube, forming the resultant work-piece into a substantially flattened and axially twistedmember correspending to one half the desired blade, and securing a substantially attened member to the resultant work-piece to form the finished blade.

3. In a method for producing a hollow metal propeller blade the steps comprising slotting a hollow tube spirally and longitudinally of its major axis, forming the spirally slotted tube into a substantially flattened blade member, and welding a substantially flattened blade piece to the blade member to form apropeller blade of airfoil section.

4. The method of manufacturing a propeller blade from a hollow tube comprising removing a longitudinally spirally formed portion of the wall of said tube, opening and pressing said tube into a blank forming a blade face, trimming one end of said blank, and securing a member to the blank to form the nished blade.

5. In the method of producing a propeller blade from a hollow metal tube, the steps oomprising slotting said tube spirally and longitudinally of its major axis, opening and pressing the slotted portion of the tube into a blade face, and securing a blade member to said slotted tube to form a hollow blade of airfoil section.

6. In a method of producing a propeller blade from a hollow metal tube, the steps comprising removing a spirally formed section of the wall of the tube the edges of said section diverging lfrom one end toward the other, shaping the resultant work-piece into a blade face, and securing a second blade face thereto to form the desired blade. l

v7. The method of producing a propeller blade from a hollow seamless metal tube comprising removing a longitudinally extending section oi the wall of the tube, opening and pressing the resultant work-piece into a substantially flattened member having a flanged marginal portion, and fusing said flanged portion to the peripheral portion of a blade member forming a blade face to form' a propeller blade of airfoil section. 8. The method of making a propeller blade from a hollow tube which comprisestapering the thickness of the wall of said tube, removing a longitudinally extending portion of the wall of said tube to form an opening divergent from one end toward the other,` opening and pressing the resultant work-piece into a substantially attened blade member adapted to form one face ofthe blade to be formed, and welding the peripheral portion of a substantially flattened plate to the marginal portion of the blade member defining said opening to form a blade of airfoil section.

9. The method of forming a hollow propeller blade from a metal tube comprising removing a section of the wall of said tube 'to form an opening therein, enlarging said opening by pressing the tube into a blade member, forming the portion of the blade defining said enlarged opening into a anged marginal portion, and welding the peripheral portion of a substantially flat blade piece to the flanged marginal portion of the blade member defining said enlarged opening, to form a propeller blade of airfoil section.

MARSHALL A. SMITH, JR. 

